Field
Embodiments described herein relate generally to an etching amount measurement pattern, etching amount measurement apparatus, and etching amount measurement method.
Description of the Related Art
In the manufacture of microstructures such as semiconductor devices, photomasks, etc., the end point of the plasma etching is detected from the change of the light emission spectrum of the plasma in the case where the etching object on which the plasma etching is to be performed includes multiple stacked layers (e.g., refer to JP-A H09-36090 (Kokai)).
However, in the case where the same material of the etching object is to be removed up to partway through the thickness, the end point detection cannot be performed based on the change of the light emission spectrum because the light emission spectrum of the plasma does not change.
Therefore, technology has been proposed in which light is irradiated on a measurement portion of the etching object where the processing end point is to be measured; and the thickness dimension (e.g., the film thickness) of the measurement portion is measured from the intensity change of coherent light (e.g., refer to JP-A H10-64884 (Kokai)).
That is, because the intensity of the coherent light and the thickness dimension of the measurement portion have a correlation, the thickness dimension of the measurement portion can be determined by sensing the intensity of the coherent light. Therefore, the fluctuation of the thickness dimension of the measurement portion during etching, that is, the etching amount, can be determined by successively sensing the intensity of the coherent light.
However, in the case where the thickness dimension of the measurement portion is determined using coherent light, problems occur because the upper limit of the measurable thickness dimension is small. In other words, in the case where the thickness dimension of the measurement portion is determined using coherent light, unfortunately, only components that are thin can be measured.
In such a case, generally, the measurement of the thickness dimension using coherent light is difficult unless the thickness dimension of the measurement portion is several tens times the wavelength of the light used in the measurement or less.
Therefore, for example, in the case where the thickness dimension of the measurement portion is 0.4 mm or more, there are cases where the measurement of the thickness dimension using coherent light and the measurement of the etching amount are difficult.
On the other hand, technology has been proposed in which the etching amount for a substrate having a thick measurement portion, etc., is measured from the light emission spectrum of light having a broad spectrum.
However, the polarization management in the wavelength range of the broad spectrum is complex. This is because the spectrum fluctuates according to the proportion of TE waves (Transverse Electric Waves) that have electric field components perpendicular to the incident direction and TM waves (Transverse Magnetic Waves) that have magnetic field components perpendicular to the incident direction.
Therefore, it is desirable to develop an etching amount measurement pattern for which the polarization management is unnecessary when measuring the etching amount using light having a broad spectrum.